In a prior art, the shape of a whole workpiece to be machined and the area to be machined, namely the designated machining area, were displayed in a screen on a CRT display unit when an operator created an NC program, used with turning machines, by means of an interactive computer system. The area to be actually machined in each machining operation by a designated tool is displayed in another screen on the CRT unit.
FIG. 1 shows a screen displaying the shape of a whole workpiece and a designated machining area in the workpiece. In the drawing, the outline of a section of the workpiece which is going to be machined is shown by a broken line, while the designated machining area is shown by a continuous thick line. The area to be actually machined, namely the area to be removed from the whole workpiece is the area less the designated machining area plus finishing stock (not shown) which is left for finishing processes from the whole workpiece. Black squares at points A and B indicate the points at which the machining area is designated. Arrows at points A and B indicate cutter feed direction for machining the workpiece. When the arrow at point B points straight up in the drawing, the designated machining area is the area 11 indicated with oblique hatched lines as shown in the drawing. When the arrow at point B points toward the upper left of the drawing, the designated machining area is the hatched area 11 plus the dotted area 12 as shown in the drawing. By the way, machining a workpiece, here, is carried out by chucking the workpiece on a spindle unit in a machine tool, turning the spindle around the Z axis and feeding a bite 1 in at least one of the directions X or Z as shown in the drawing.
FIG. 2 shows a screen displaying a designated machining area and an outline of a workpiece before machining the workpiece by designated tool No. 1. In the drawing, TX and TZ indicate the finishing stock, namely the width of stock to be left after completion of the machining of the workpiece in the directions X and Z respectively. The designated machining area shown by a continuous thick line plus the finishing stock is the desired shape of a part after the completion of the first machining of the workpiece. However, the actual shape of the workpiece after the machining by the designated tool No. 1 under conditions concerning, for example, the finishing stock, the cutting conditions for the tool or the like is as shown by a continuous thin line. It can be understood from the drawing that there are some uncut areas when the shape shown by the continuous thin line is compared with the desired shape of the workpiece shown by the thick line. In order to machine the workpiece to a desired finished shape, it is necessary to find the uncut area by comparing two screens shown by FIG. 1 and FIG. 2 and to machine the found uncut area by means of another tool. The process for accomplishing this will be explained below.
FIG. 3 shows a screen displaying a designated machining area of a workpiece after completion of the first machining by the designated tool No. 1 and the shape of the machining area to be machined by the designated tool No. 2. This screen is displayed when an operator creating an NC program designates the area to be machined and the tool for machining the same area before machining an uncut area which is left after completion of the machining by the designated tool No. 1. In the drawing, the hatched area indicates a first portion of the uncut area which could not be machined by the designated tool No. 1. Black squares at points C and D indicate the points for designating machining areas, and arrows at the points C and D indicate cutter feed directions for machining the workpiece. After inspecting the new shape for machining the designated machining area, the designated tool No. 2 will be selected.
FIG. 4 shows a screen displaying a designated machining area of a workpiece after completion of the first machining by the designated tool No. 1 and the second machining by the designated tool No. 2, and the shape of a second uncut portion of the machining area to be machined by the designated tool No. 3. This screen is displayed when an operator designates the area to be machined and the tool for machining the same area before machining an uncut area which is left after completion of the machining by the designated tools No. 1 and No. 2. In the drawing, the hatched area indicates the uncut area which could not be machined by the designated tools No. 1 and No. 2. Black squares at points E and F indicate the points for designating machining areas, and arrows at the points E and F indicate cutter feed direction for machining the workpiece. After inspecting the new shape for machining the designated machining area, the designated tool No. 3, using for grooving, will be selected.
As heretofore explained, the method for defining machining areas of a workpiece in a CRT screen display of the prior art has a problem in that the area actually completed by the machining is unclear because the screen according to prior art does not show an overlapped view of the shape of the whole workpiece before machining and the shape of the workpiece after completion of the machining for each designated machining area by the designated tool.